1. Field of the Invention
The present invention relates to a wireless communication terminal and QoS information collection method.
2. Related Background Art
An adhoc network is constituted by autonomous user terminals e.g., personal digital assistants (PDA), personal computers, wireless communication terminals such as cellular phones, and links among the respective wireless communication terminals. A base station, an access point and so forth that manages the wireless communication terminals does not exist in this adhoc network. Therefore, routing is required by each of the wireless communication terminals before starting communications. As a result of the routing, it is determined where the communication-destination wireless communication terminal is and which wireless communication terminal communications are to be routed through for communication with the terminal. The protocols for routing in such ad-hoc networks include the proactive-type routing protocol, for example.
In a proactive-type routing protocol, the respective wireless communication terminals have a routing table for storing path information to other wireless communication terminals on the network. Here, the path information stored in the routing table is found as follows, for example. First, the topology, which is the connection form of the network, is determined on the basis of topology information that is exchanged at fixed intervals between the respective wireless communication terminals. Path information to the other wireless communication terminals is then found on the basis of the topology. By using a routing table in which such path information is stored, the respective wireless communication terminals are always able to grasp the path to the respective transmission destinations irrespective of whether communication exists.
In an adhoc network of this kind, because the states of the links change at any time unlike a wired network, the communication quality such as the bandwidth and delay and so forth also accordingly changes at any time. Hence, in an adhoc network requiring a high communication quality, information on the existence of a link as well as link QoS (Quality of Service) information must be exchanged between the respective wireless communication terminals.
When QoS information is exchanged by using an proactive-type routing protocol, the topology information is exchanged at fixed intervals between the respective wireless communication terminals after the QoS information on the links has also been added to the information on the existence of links contained in the topology information (See Document 1: ‘Hakim Badis, Anelise Munaretto, Khaldoun Al Agha and Guy Pujolle, “QoS for Ad-hoc Networking Based on Multiple Metrics: Bandwidth and Delay”, In the Proceedings of the 5th IFIP TC6 International Conference on Mobile and Wireless Communication Networks (MWCN'03), IEEE, Singapore, October 2003.’ and Document 2 ‘Ying Ge, Thomas Kunz and Louise Lamont, “Quality of Service Routing in Ad-hoc Networks Using OLSR”, in the Proceedings of the 36th Hawaii International Conference on System Sciences (HICSS'03), IEEE, 2003.’ As a result, a path to the transmission destination can be constructed by the respective wireless communication terminals and the quality of the path can be judged. Hence, when a plurality of paths to the transmission destination exist, communication can be performed by selecting the path with the optimum quality.
Further, when QoS information that uses the proactive-type routing protocol is exchanged, QoS information on the links is also added to the topology information exchanged at fixed intervals. Hence, the amount of consumption of terminal resources such as the CPU and memory and wireless resources such as the communication bandwidth increases and the load on the network increases.